The kibibyte is a multiple of the unit byte for quantities of digital information. The binary prefixkibi means 1024, therefore 1 kibibyte is 1024 bytes. The unit symbol for the kibibyte is KiB.[1]

The unit was established by the International Electrotechnical Commission (IEC) in 1998,[2] has been accepted for use by all major standards organizations, and is part of the International System of Quantities.[3] The kibibyte was designed to replace the kilobyte in those computer science contexts in which the term kilobyte is used to mean 1024 bytes. The interpretation of the kilobyte to denote 1024 bytes, conflicting with the SI definition of the prefix kilo (1000), is still common, mostly in informal computer science contexts.

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The prefix kibi is derived as a portmanteau of the words kilo and binary, indicating its origin in the closeness in value to the SI prefixkilo (1000). While the SI prefix is written with lowercase (k), all IEC binary prefixes use an uppercase letter.[1][not in citation given]

The kibibyte is closely related to the kilobyte. The latter term is often used in some contexts as a synonym for kibibyte, but formally refers to 103 bytes = 1000 bytes, as the prefix kilo is defined in the International System of Units.

Donald Knuth proposed to call this unit a large kilobyte (KKB).[4] Other early proposals included using the Greek lowercase letter κ (kappa) for 1024 bytes (and using k exclusively for 1000), bK, KB, and others.

IEC binary prefixes are increasingly used, especially in scientific literature and open source software. In product advertising and other non-scientific publications, the kilobyte sometimes refers to a power of ten and sometimes a power of two.[5][6][7]